Tinted lenses are often used to protect a user from high levels of ambient light and glare. The tint of the lens decreases the amount of light transmitted through the lens. Glare is defined as light of sufficient brightness transmitted to an eye or optical sensor such that vision or detection is impaired. In the case of a human eye, blurring of vision, physical pain, or ocular fatigue may also be experienced when exposed to glare. Glare may be transmitted from light reflected from a surface. Surfaces may include for example, windshields, windows, water, snow, and metal.
Tinted lenses may also be polarized to protect the user from glare. Reflected light is polarized, but ambient light is not polarized. Blocking polarized light allows the lenses to block additional glare without decreasing non-polarized light transmitted through the lens, for example, by using a darker tint. This prevents the lenses from inhibiting a user's vision in lower light conditions when glare may still be present. For example, at sunrise, light may reflect strongly off a body of water, but the surrounding area may not yet be well-lit by the rising sun.
Some tinted lenses may decrease a user's ability to discriminate colors based on the light transmitted through the lens. This may be undesirable as it may prevent the user from distinguishing objects based on color. This reduced ability of a user to discriminate between colors may also be referred to as color confusion. It may also be uncomfortable to the user to view familiar objects in unfamiliar hues.